<?php
/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_Search_Lucene
 * @subpackage Index
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @version    $Id: TermStreamsPriorityQueue.php 18947 2009-11-12 11:57:17Z alexander $
 */

/** Zend_Search_Lucene_Index_TermsStream_Interface */
require_once 'Zend/Search/Lucene/Index/TermsStream/Interface.php';


/**
 * @category   Zend
 * @package    Zend_Search_Lucene
 * @subpackage Index
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_Search_Lucene_TermStreamsPriorityQueue implements Zend_Search_Lucene_Index_TermsStream_Interface
{
	/**
	 * Array of term streams (Zend_Search_Lucene_Index_TermsStream_Interface objects)
	 *
	 * @var array
	 */
	protected $_termStreams;

	/**
	 * Terms stream queue
	 *
	 * @var Zend_Search_Lucene_Index_TermsPriorityQueue
	 */
	protected $_termsStreamQueue = null;

	/**
	 * Last Term in a terms stream
	 *
	 * @var Zend_Search_Lucene_Index_Term
	 */
	protected $_lastTerm = null;


	/**
	 * Object constructor
	 *
	 * @param array $termStreams  array of term streams (Zend_Search_Lucene_Index_TermsStream_Interface objects)
	 */
	public function __construct(array $termStreams)
	{
		$this->_termStreams = $termStreams;

		$this->resetTermsStream();
	}

	/**
	 * Reset terms stream.
	 */
	public function resetTermsStream()
	{
		/** Zend_Search_Lucene_Index_TermsPriorityQueue */
		require_once 'Zend/Search/Lucene/Index/TermsPriorityQueue.php';

		$this->_termsStreamQueue = new Zend_Search_Lucene_Index_TermsPriorityQueue();

		foreach ($this->_termStreams as $termStream) {
			$termStream->resetTermsStream();

			// Skip "empty" containers
			if ($termStream->currentTerm() !== null) {
				$this->_termsStreamQueue->put($termStream);
			}
		}

		$this->nextTerm();
	}

	/**
	 * Skip terms stream up to specified term preffix.
	 *
	 * Prefix contains fully specified field info and portion of searched term
	 *
	 * @param Zend_Search_Lucene_Index_Term $prefix
	 */
	public function skipTo(Zend_Search_Lucene_Index_Term $prefix)
	{
		$termStreams = array();

		while (($termStream = $this->_termsStreamQueue->pop()) !== null) {
			$termStreams[] = $termStream;
		}

		foreach ($termStreams as $termStream) {
			$termStream->skipTo($prefix);

			if ($termStream->currentTerm() !== null) {
				$this->_termsStreamQueue->put($termStream);
			}
		}

		$this->nextTerm();
	}

	/**
	 * Scans term streams and returns next term
	 *
	 * @return Zend_Search_Lucene_Index_Term|null
	 */
	public function nextTerm()
	{
		while (($termStream = $this->_termsStreamQueue->pop()) !== null) {
			if ($this->_termsStreamQueue->top() === null ||
			$this->_termsStreamQueue->top()->currentTerm()->key() !=
			$termStream->currentTerm()->key()) {
				// We got new term
				$this->_lastTerm = $termStream->currentTerm();

				if ($termStream->nextTerm() !== null) {
					// Put segment back into the priority queue
					$this->_termsStreamQueue->put($termStream);
				}

				return $this->_lastTerm;
			}

			if ($termStream->nextTerm() !== null) {
				// Put segment back into the priority queue
				$this->_termsStreamQueue->put($termStream);
			}
		}

		// End of stream
		$this->_lastTerm = null;

		return null;
	}

	/**
	 * Returns term in current position
	 *
	 * @return Zend_Search_Lucene_Index_Term|null
	 */
	public function currentTerm()
	{
		return $this->_lastTerm;
	}

	/**
	 * Close terms stream
	 *
	 * Should be used for resources clean up if stream is not read up to the end
	 */
	public function closeTermsStream()
	{
		while (($termStream = $this->_termsStreamQueue->pop()) !== null) {
			$termStream->closeTermsStream();
		}

		$this->_termsStreamQueue = null;
		$this->_lastTerm         = null;
	}
}
